Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

AKT has a critical role in relaying cell survival and proliferation signals initiated by ligand binding to surface receptors in mammalian cells. Induction of AKT serine/threonine kinase activity is augmented by the T-cell leukemia-1 (TCL1) oncoprotein through a physical association requiring the AKT pleckstrin homology domain. Here, we used molecular modeling and identified an exposed hydrophobic patch composed of two discontinuous amino acid stretches near one end of the TCL1 beta-barrel that was required for a TCL1-AKT association. Site-directed mutations of this region did not affect TCL1 secondary structure, yet they disrupted interactions with AKT. This region was found in other members of the TCL1 oncoprotein family, such as TCL1b and MTCP1, and suggested a conserved, novel AKT binding domain. Interestingly, TCL1 and AKT co-localize in multiple cell compartments, but only extracts from the plasma membrane stimulate optimal complex formation in vitro. Identification of an AKT binding domain on TCL1 is an important step in deciphering the complex interactions that regulate AKT kinase activity in lymphocyte development and neoplasia within the immune system.
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PMID:A modeled hydrophobic domain on the TCL1 oncoprotein mediates association with AKT at the cytoplasmic membrane. 1200 99

Plexins represent a novel family of transmembrane receptors that transduce attractive and repulsive signals mediated by the axon-guiding molecules semaphorins. Emerging evidence implicates Rho GTPases in these biological events. However, Plexins lack any known catalytic activity in their conserved cytoplasmic tails, and how they transduce signals from semaphorins to Rho is still unknown. Here we show that Plexin B2 associates directly with two members of a recently identified family of Dbl homology/pleckstrin homology containing guanine nucleotide exchange factors for Rho, PDZ-RhoGEF, and Leukemia-associated Rho GEF (LARG). This physical interaction is mediated by their PDZ domains and a PDZ-binding motif found only in Plexins of the B family. In addition, we show that ligand-induced dimerization of Plexin B is sufficient to stimulate endogenous RhoA potently and to induce the reorganization of the cytoskeleton. Moreover, overexpression of the PDZ domain of PDZ-RhoGEF but not its regulator of G protein signaling domain prevents cell rounding and neurite retraction of differentiated PC12 cells induced by activation of endogenous Plexin B1 by semaphorin 4D. The association of Plexins with LARG and PDZ-RhoGEF thus provides a direct molecular mechanism by which semaphorins acting on Plexin B can control Rho, thereby regulating the actin-cytoskeleton during axonal guidance and cell migration.
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PMID:Plexin B regulates Rho through the guanine nucleotide exchange factors leukemia-associated Rho GEF (LARG) and PDZ-RhoGEF. 1218 58

B-cell-specific plasma-membrane proteins are potential targets for either small molecule or antibody-based therapies. We have sought to annotate proteins expressed at the cell surface membrane in patients with chronic lymphocytic leukemia (CLL) using plasma-membrane-based proteomic analysis to identify previously uncharacterized and potentially B-cell-specific proteins. Proteins from plasma-membrane fractions were separated on one-dimensional gels and trypsinized fractions subjected to high-throughput MALDI-TOF mass spectrometry. Using this method, many known B-cell surface antigens were detected, but also known proteins not previously described in this disease or in this cellular compartment, including cell surface receptors, membrane-associated enzymes and secreted proteins, and completely unknown proteins. To validate the method, we show that BLK, a B-cell-specific kinase, is located in the CLL-plasma-membrane fraction. We also describe two novel proteins (MIG2B and B-cell novel protein #1, BCNP1), which are expressed preferentially in B cells. MIG2B is in a highly conserved and defined gene family containing two plasma-membrane-binding ezrin/radixin/moesin domains and a pleckstrin homology domain; the Caenorhabditis elegans homolog (UNC-112) is a membrane-associated protein that colocalizes with integrin at cell-matrix adhesion complexes. BCNP1 is a completely unknown protein with three predicted transmembrane domains, with three alternatively spliced final exons. Proteomic analysis may thus define new potential therapeutic targets.
Leukemia 2003 Aug
PMID:Proteomic analysis of the cell-surface membrane in chronic lymphocytic leukemia: identification of two novel proteins, BCNP1 and MIG2B. 1288 50

G alpha 12/13-mediated pathways have been shown to be involved in various fundamental cellular functions in mammalian cells such as axonal guidance, apoptosis, and chemotaxis. Here, we identified a homologue of Rho-guanine nucleotide exchange factor (GEF) in Caenorhabditis elegans (CeRhoGEF), which functions downstream of gpa-12, the C. elegans homologue of G alpha 12/13. CeRhoGEF contains a PSD-95/Dlg/ZO-1 domain and a regulator of G protein signaling (RGS) domain upstream of the Dbl homology-pleckstrin homology region similar to mammalian RhoGEFs with RGS domains, PSD-95/Dlg/ZO-1-RhoGEF and leukemia-associated RhoGEF. It has been shown in mammalian cells that these RhoGEFs interact with activated forms of G alpha 12 or G alpha 13 through their RGS domains. We demonstrated by coimmunoprecipitation that the RGS domain of CeRhoGEF interacts with GPA-12 in an AIF4- activation-dependent manner and confirmed that the Dbl homology-pleckstrin homology domain of CeRhoGEF was capable of Rho-dependent signaling. These results proved conservation of the G alpha 12-RhoGEF pathway in C. elegans. Expression of DsRed or GFP under the control of the promoter of CeRhoGEF or gpa-12 revealed an overlap of their expression patterns in ventral cord motor neurons and several neurons in the head. RNA-mediated gene interference for CeRhoGEF and gpa-12 resulted in similar phenotypes such as embryonic lethality and sensory and locomotive defects in adults. Thus, the G alpha 12/13-RhoGEF pathway is likely to be involved in embryonic development and neuronal function in C. elegans.
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PMID:Identification and molecular characterization of the G alpha12-Rho guanine nucleotide exchange factor pathway in Caenorhabditis elegans. 1465 63

Chromosomal translocations leading to overexpression of p14(TCL1) and its homologue p13(MTCP1) are hallmarks of several human T-cell malignancies (1). p14(TCL1)/p13(MTCP1) co-activate protein kinase B (PKB, also named Akt) by binding to its pleckstrin homology (PH) domain, suggesting that p14(TCL1)/p13(MTCP1) induce T-cell leukemia by promoting anti-apoptotic signals via PKB (2, 3). Here we combined fluorescence anisotropy, NMR, and small angle x-ray-scattering measurements to determine the affinities, molecular interfaces, and low resolution structure of the complex formed between PKBbeta-PH and p14(TCL1)/p13(MTCP1). We show that p14(TCL1)/p13(MTCP1) target PKB-PH at a site that has not yet been observed in PH-protein interactions. Located opposite the phospholipid binding pocket and distal from known protein-protein interaction sites on PH domains, the binding of dimeric TCL1 proteins to this site would allow the crosslinking of two PKB molecules at the cellular membrane in a preactivated conformation without disrupting certain PH-ligand interactions. Thus this interaction could serve to strengthen membrane association, promote trans-phosphorylation, hinder deactivation of PKB, and involve PKB in a multi-protein complex, explaining the array of known effects of TCL1. The binding sites on both proteins present attractive drug targets against leukemia caused by TCL1 proteins.
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PMID:Structural basis for the co-activation of protein kinase B by T-cell leukemia-1 (TCL1) family proto-oncoproteins. 1516 87

Guanine nucleotide exchange factors (GEFs) of the Dbl family activate Rho proteins and thereby participate in diverse signaling pathways involving this family of small GTPases. However, specific role of Dbl-GEFs in developmental processes, particularly cell differentiation, remains largely unexplored. Recently, a novel member of the Dbl family, leukemia-associated Rho GEF factor (LARG), has been reported to be a fusion partner with mixed-lineage leukemia (MLL) protein in the acute myeloid leukemia, suggesting potential involvement of LARG in regulation of hematopoiesis. In this study, we describe the isolation of the cDNA copy and analysis of genomic structure and expression profile of the mouse orthologue of the human LARG gene. The mouse LARG (mLARG) gene contains 42 exons. The mLARG cDNA is 10,040 bp long and contains a 4631-bp open reading frame (ORF). The predicted mLARG protein shares an overall 89% identity with its human counterpart and contains the same functional domains, namely, Dbl homology (DH), pleckstrin homology (PH), PSD-95, Dlg and ZO-1/2 (PDZ) and regulator of G protein signaling (RGS) domains, as well as two putative signals of nuclear localization. The mLARG message is expressed in all tissues studied, with comparably higher expression levels observed in brain, lung, testis, liver and heart. Using amplified cDNA samples from sorted hematopoietic cells, we showed that mLARG is highly expressed in hematopoietic stem cell fractions, as well as in immature erythroid cells. These results demonstrate high similarity between mouse and human LARG proteins and genes and provide further support to the hypothesis of the potential involvement of LARG in regulation of early stages of hematopoiesis.
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PMID:Molecular cloning, sequence and expression pattern analysis of the mouse orthologue of the leukemia-associated guanine nucleotide exchange factor. 1527 14

Several oncogenes isolated by the NIH/3T3 transformation assay, i.e., dbl, dbs, lbc, lfc, lsc, net, ost and tim, contain a Dbl homology (DH) and a pleckstrin-homology (PH) domain and act as GEFs (guanine nucleotide exchange factors) for Rho-like GTPases. In a search for genes with oncogenic potential in DNA from the monocytic leukaemia cell line U937, we identified an amino-terminal truncated form of gef-h1, a gene encoding a GEF for RhoA. These data support the idea that a systematic search for mutations and/or deletions of GEFs in human cancer is promising.
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PMID:Activation of gef-h1, a guanine nucleotide exchange factor for RhoA, by DNA transfection. 1545 75

A balanced translocation t(12;16)(p13;p13) in a patient with AML-M1 and bone marrow eosinophilia was previously analysed by FISH. The 16p13 breakpoint was shown to occur in the MYH11 gene, the fusion partner of CBFbeta in leukaemia patients with an inv(16) or a t(16;16), whereas the 12p13 breakpoint was shown to be present in cosmid c4H9. We present the molecular analysis of c4H9, resulting in the identification of a novel gene, SLAG. At the N-terminus, SLAG contains a Sec7 domain also found in proteins of the cytohesin family. In contrast to the cytohesins, no pleckstrin homology domain is present in SLAG. database searches identified several homologues, suggesting that SLAG defines a new subfamily of Sec7 proteins, characterised by an N-terminal Sec7 domain and a new C-terminal pleckstrin homology-like domain. The FISH data led to the hypothesis that rearrangement of SLAG might be involved in the pathogenesis of AML through the generation of a new fusion gene with MYH11. However, the putative SLAG-MYH11 fusions showed only weak transforming properties in NIH3T3 cells in a focus formation assay.
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PMID:The der(12)t(12;16) breakpoint in an acute leukaemia case targets a Sec7 domain containing protein. 1575 9

Among peripheral T-cell lymphomas (PTCL), the heterogeneous category of unspecified PTCL represents the most common subtype. Nevertheless, recurrent chromosomal translocations are unknown in this aggressive type of lymphoma. Here we describe a novel t(5;9)(q33;q22) in unspecified PTCL. Molecular analyses delineated the breakpoints to ITK and SYK resulting in a previously undescribed expression of the Syk tyrosine kinase by Itk. ITK-SYK transcripts were detected in five of 30 (17%) unspecified PTCL, but not in cases of angioimmunoblastic T-cell lymphoma (n=9) and anaplastic lymphoma kinase-negative anaplastic large-cell lymphoma (n=7). In all five translocation-positive cases, the breakpoints were identical fusing the N-terminal pleckstrin homology domain and proline-rich region of ITK to the tyrosine kinase domain of SYK. Three of the five t(5;9)(q33;q22)+ unspecified PTCL shared a very similar histological pattern with predominant involvement of lymphoid follicles and the same CD3+CD5+CD4+bcl-6+CD10+ immunophenotype. These results demonstrate the presence of a recurrent t(5;9)(q33;q22) in a subset of unspecified PTCL, which may represent a novel distinct subgroup of PTCL.
Leukemia 2006 Feb
PMID:Novel t(5;9)(q33;q22) fuses ITK to SYK in unspecified peripheral T-cell lymphoma. 1630 12

Serine threonine kinase Akt, also called PKB (protein kinase B), plays a central role in regulating intracellular survival. Deregulation of this Akt signaling pathway underlies various human neoplastic diseases. Recently, the proto-oncogene TCL1 (T cell leukemia 1), with a previously unknown physiological function, was shown to interact with the Akt pleckstrin homology domain, enhancing Akt kinase activity; hence, it functions as an Akt kinase coactivator. In contrast to pathological conditions in which the TCL1 gene is highly activated in various human neoplasmic diseases, the physiological expression of TCL1 is tightly limited to early developmental cells as well as various developmental stages of immune cells. The NBRE (nerve growth factor-responsive element) of the proximal TCL1 promoter sequences can regulate the restricted physiological expression of TCL1 in a negative feedback mechanism. Further, based on the NMR structural studies of Akt-TCL1 protein complexes, an inhibitory peptide, "Akt-in," consisting of the betaA strand of TCL1, has been identified and has therapeutic potential. This review article summarizes and discusses recent advances in the understanding of TCL1-Akt functional interaction in order to clarify the biological action of the proto-oncogene TCL1 family and the development avenues for a suppressive drug specific for Akt, a core intracellular survival regulator.
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PMID:Proto-oncogene TCL1: more than just a coactivator for Akt. 1736 Aug 49


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